The invention relates to convertors for converting data given in digital form into data in analog form.
Such a convertor may be used by itself in order to have available data in analog form. It may also form a part of an analog-to-digital convertor in which it is used for transforming digital output data given by a reversible counter into auxiliary analog data, the reversible counter being driven by the difference between that auxiliary analog data and the input analog data to be converted.
More and more applications are being found for digital-to-analog and analog-to-digital convertors because of the advantage of transmission of data in digital form.
In certain applications, a linear conversion is not satisfactory. Thus, in telephony, a linear conversion would lead to intolerable quantification noises. As the installing at each subscriber set of an analog-to-digital convertor and of a digital-to-analog convertor is anticipated, there arises the problem of providing non-linear convertors which are not very expensive, which may follow a predetermined data expansion or compression law.
The problem which arises in telephony is found again in certain calculating operations such as the extraction of square roots and in numerous other applications of digital-to-analog and analog-to-digital convertors.
In these applications, the ideal relation which should be established between the digital data and the analog data is known, that relation resulting in a curve which may, with a certain approximation, be related to a sequence of segments of straight lines. It is thus possible to distribute the various possible values of the digital data into a certain number of ranges, in such a way that within a same range, the relation between the analog data and the digital data of a convertor will be linear.